Send emails with Python and Gmail SMTP server

python_emails.py

# main.py
# Import section ....
import os
import sys
from dotenv import load_dotenv
from smtplib import SMTP, SMTPException # Import SMTP module
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
import email.encoders

# Loading ENV variables
load_dotenv()

# Constants section ....

# GMAIL account sender
SENDER = os.getenv('SENDER')
PASSWORD = os.getenv('PASSWORD')

# Accounts receivers
RECEIVERS = os.getenv('RECEIVERS').split(',')

# SMTP server options
HOST = os.getenv('HOST')
PORT = os.getenv('PORT')

# ....
# SMTP object
SMTP_OBJECT = SMTP(host=HOST, port=PORT)

# Methods section ....

# Base function
def send_email(message=""):
    """
    Send an email using the credentials defined before
    
    Parameters
    ----------
    message : str
	    content to send in the message
    """
    try:
        SMTP_OBJECT.ehlo()
        SMTP_OBJECT.starttls()
        SMTP_OBJECT.login(SENDER, PASSWORD)
        SMTP_OBJECT.sendmail(SENDER, RECEIVERS, message)
        SMTP_OBJECT.quit()
        print("Successfully sent email")
    except SMTPException:
        print ("Error: unable to send email")

def basic_email(message = ""):
    """
    Basic email with plain text message
    """
    send_email(message)

def send_from_txt():
    """
    Send an email reading the content message from a txt file
    """
    message = MIMEMultipart('alternative')
    message['Subject'] = 'TXT file content'
    message['From'] = SENDER
    body = "Email message body"
    content = MIMEText(body, 'plain')
    message.attach(content)

    # process text file
    file_open = open('text.txt', 'rb')
    file_content = MIMEText(_text=file_open.read(), _charset='utf-8')
    file_open.close()
    message.attach(file_content)

    # Send email
    send_email(message.as_string())

def send_attachment():
    """
    Send an email with an attachment
    """
    message = MIMEMultipart('alternative')
    message['Subject'] = 'Attachment'
    message['From'] = SENDER

    attachment = MIMEBase('application', 'octet-stream')
    attachment.set_payload(open('file.pdf', 'rb').read())
    attachment.add_header('Content-Disposition', 'attachment; filename="file.pdf"')

    email.encoders.encode_base64(attachment)
    message.attach(attachment)

    # Send email
    send_email(message.as_string())

# Main section ...
if __name__ == "__main__":
    # Message to send
    message = """
    this message is sent from python for testing purposes
    """
    
    if len(sys.argv)> 1 :
        if sys.argv[1] == '--help':
            print('Info: ')
            print('--help List the options to send an email')
            print('--basic Sends a plain text email')
            print('--txt Send an email from a text file content')
            print('--attach Send an email with an attachment')
        elif sys.argv[1] == '--basic':
            print("Sending a plain text email")
            basic_email(message)
        elif sys.argv[1] == '--txt':
            print("Sending an email from a text file content")
            send_from_txt()
        elif sys.argv[1] == '--attach':
            print("Sending an email with an attachment")
            send_attachment()
    else:
        print("Please give the type of message to send.")
        print("For help execute `python main.py --help`")